The objectives of this research are to investigate the formal genetics of Dictyostelium discoideum and to use mutants to investigate developmental problems. The formal genetics will be concerned with collecting drug resistant mutants, mapping them and using them in the construction of a tester stock. The latter will be used for the rapid assignment of new mutants to their proper linkage group. We will also continue our analysis of aberrant segregants in the hope of proving our mitotic recombination model. Finally we hope to examine the relationship between mating types in Dictyostelium and both sexual and parasexual cycles. Our developmental studies are centered around our investigation of the cell cycle in Dictyostelium. We will investigate the relationship between the cell cycle and the control of aggregation. In particular, we want to know the relative importance of starvation and a mid-G2 block in the control of aggregation. This will be investigated firstly by seeing if amoebae can aggregate at phases of the cell cycle other than G2. It will also be investigated by assaying for the molecules involved in the aggregation process and examining the pattern of proteins synthesized between starvation and aggregation. Finally, we will examine the role that the cell cycle plays in the process of sorting out.